1. Field of the Invention
The present invention relates to a method and an apparatus for grinding a workpiece, specifically, for grinding an outer peripheral edge of a workpiece formed of a circular thin plate such as a semiconductor wafer.
2. Description of the Related Art
Conventionally, in a case where this type of workpiece formed of a circular thin plate is ground, a grinding method such as the one shown in FIG. 16 has been adopted. Namely, in this conventional method, a workpiece 71 is rotated about its center as an axis L1, and a forming grinding wheel 72 is moved so as to be fed toward an outer peripheral edge portion 71a of the workpiece 71 while being rotated about an axis L2 which is parallel to the central axis L1 of the workpiece 71. As a result, the outer peripheral edge portion 71a of the workpiece 71 is ground by a recessed wheel surface 72a of the outer periphery of the forming grinding wheel 72.
However, with this conventional method of grinding a workpiece, since the outer peripheral edge portion 71a of the workpiece 71 is arranged to be ground at one time by the recessed wheel surface 72a of the forming grinding wheel 72, the recessed wheel surface 72a of the forming grinding wheel 72 has been liable to become worn, and the deformation of its profile has been liable to occur as a result. For this reason, particularly in finishing, it is extremely difficult to maintain constant the machining accuracy of the profiles of the outer peripheral edge portions 71a of a multiplicity of workpieces 71 by a single forming grinding wheel 72, and it has been necessary to replace the forming grinding wheel 72 frequently, so that there have been problems in terms of the machining accuracy and machining cost.